diff --git a/conftest.py b/conftest.py
index 3e2008c..fe68ac5 100644
--- a/conftest.py
+++ b/conftest.py
@@ -1,7 +1,5 @@
 import pytest
 
-import jaraco.path
-
 
 @pytest.fixture(autouse=True)
 def _isolate_home(tmp_home_dir):
@@ -25,20 +23,14 @@ def _isolate_home(tmp_home_dir):
 @pytest.fixture
 def hg_repo(hg_repo):
     repo = hg_repo
-    jaraco.path.build(rev1)
-    repo._invoke('addremove')
-    repo._invoke('ci', '-m', 'committed')
-    jaraco.path.build(rev2)
-    repo._invoke('ci', '-m', 'added content')
+    repo.commit_tree(rev1, 'committed')
+    repo.commit_tree(rev2, 'added content')
     return repo
 
 
 @pytest.fixture
 def git_repo(git_repo):
     repo = git_repo
-    jaraco.path.build(rev1)
-    repo._invoke('add', '.')
-    repo._invoke('commit', '-m', 'committed')
-    jaraco.path.build(rev2)
-    repo._invoke('commit', '-am', 'added content')
+    repo.commit_tree(rev1, 'committed')
+    repo.commit_tree(rev2, 'added content')
     return repo
diff --git a/jaraco/vcs/base.py b/jaraco/vcs/base.py
index 1296f6c..bac42ea 100755
--- a/jaraco/vcs/base.py
+++ b/jaraco/vcs/base.py
@@ -134,3 +134,9 @@ def age(self):
         Return the age of the repo.
         """
         raise NotImplementedError()
+
+    def commit_tree(self, spec, msg="committed"):
+        """
+        Apply the tree in spec and commit.
+        """
+        raise NotImplementedError()
diff --git a/jaraco/vcs/cmd.py b/jaraco/vcs/cmd.py
index 6eb4626..b7c5249 100644
--- a/jaraco/vcs/cmd.py
+++ b/jaraco/vcs/cmd.py
@@ -6,6 +6,7 @@
 import subprocess
 
 import dateutil.parser
+import jaraco.path
 from tempora import utc
 
 
@@ -150,6 +151,11 @@ def sub_paths(self):
     def _get_timestamp_str(self, rev):
         return self._invoke('log', '-l', '1', '--template', '{date|isodate}', '-r', rev)
 
+    def commit_tree(self, spec, message: str = 'committed'):
+        jaraco.path.build(spec)
+        self._invoke('addremove')
+        self._invoke('commit', '-m', message)
+
 
 class Git(Command):
     exe = 'git'
@@ -225,3 +231,8 @@ def age(self):
         proc.wait()
         proc.stdout.close()
         return utc.now() - dateutil.parser.parse(first_line)
+
+    def commit_tree(self, spec, message: str = 'committed'):
+        jaraco.path.build(spec)
+        self._invoke('add', '.')
+        self._invoke('commit', '-m', message)